Validation of cleavage-specific antibodies Htt513 and Htt552. A, Western blot of wild-type murine cortical tissue demonstrating detection of a single htt fragment ending at either amino acid 513 or 552 that is present only after ex vivo cleavage of endogenous htt with recombinant caspase-3.B, Immunofluorescence of HEK 293T cells transfected with htt constructs as indicated, demonstrating that the Htt513 or Htt552 antibodies detect htt only after tamoxifen (tam)-induced cleavage or, for Htt513, in the presence of constructs terminating at amino acid 513 (H-15X), in red. Nuclei are counterstained with DAPI (blue).